The present invention relates generally to techniques for imaging an object in or behind a scattering medium and more particularly to a novel technique for imaging an object in or behind a scattering medium.
An object embedded in a highly scattering random medium cannot be easily observed because multiple light scattering randomizes the signal light direction. Objects hidden in random scattering media are common in nature, and developing a simple technique to see such hidden objects is important for many fields. In medicine, for example, it is highly desirable to image the tumor hidden in a breast by using light instead of x-rays. An optical imaging method called transillumination or diaphanography has been developed. In this method, light is incident upon the breast, and the transmitted light is measured. A shadow of the tumor may be observed because the absorption and scattering characteristics of the tumor are different from those of the normal tissue. Typically, a tumor of 1-cm diameter can be detected. However, multiple light scattering in the breast blurs the image and may result in making the tumor unrecognizable, especially when the tumor is too small or lies too deep in the breast. Recently, ultrafast laser technology was used to enhance the image by time gating the ballistic component of the laser pulses and eliminating the diffuse pulse from detection. This time-gating technique has been used by various groups to enhance the image of an object hidden in the random medium.
Publications of interest to the present invention include Yoo et al., Optics Letters, Vol. 16, No. 16, 1252-1254 (1991); Andersson-Engels et al., Optics Letters, Vol. 15, No. 21, pp. 1179-1181 (1990); Maarek et al., Medical & Biological Engineering & Computing, pp. 407-414 (July 1986); Wang et al., Science, Vol. 253, pp. 769-771 (1991); Alfano et al., Physics World, pp. 37-40 (January 1992); and Wist et al., "A Light Imaging Technique for the Improved Detection of Breast Cancer," Eighth Southern Biomedical Engineering Conference, Richmond, Virginia (Oct. 15-16, 1989).
Patents of interest to the present invention include U.S. Pat. No. 5,140,463 to Yoo et al., issuing Aug. 18, 1992 (U.S. Ser. No. 07/489,942, filed Mar. 8, 1990); U.S. Pat. No. 4,945,239 to Wist et al., which issued Jul. 31, 1990; U.S. Pat. No. 4,115,699 to Mizuta et al., which issued Sep. 19, 1978; U.S. Pat. No. 4,515,165 to Carroll, which issued May 7, 1985; U.S. Pat. No. 4,707,128 to Coles, which issued Nov. 17, 1987; U.S. Pat. No. 4,212,306 to Mahmud, which issued Jul. 15, 1980; and U.S. Pat. No. 4,570,638 to Stoddart et al., which issued Feb. 18, 1986.